In the state of the art, there are a plurality of devices and apparatus to coil strip or sheet leaving the hot or cold rolling train, which perform their function more or less efficiently.
One type of coiling machine particularly used in the hot rolling of strip or sheet is the downcoiler, which includes at least two coiling mandrels arranged in sequence and below the plane on which the strip or sheet which has to be coiled passes.
This coiling system, although it is widely used, has problems both regarding the speed at which the coils are formed and also regarding the quality of the sheet obtained, especially in the case of products which are particularly thin.
In fact, in the case of thin strip or sheet, when the leading end is bent under the plane on which it is fed in order to be coiled onto the downcoiler, there may be problems caused in the quality of the product.
Moreover, coiling is not carried out in a repetitive manner since it is performed alternately on two downcoilers placed at different distances from the shears.
Another problem which is also linked to the thinness of the strip or sheet to be coiled is that the strip rubs against the runway which delivers it to the coiling machine, which can cause a deterioration in the surface quality of the strip or sheet.
Another problem is that with the systems known in the state of the art with a guide belt for initial winding, the winding speeds must necessarily remain low. A further problem is the lead-in of the strip during the initial winding step when thin strip is being produced.
A further disadvantage is the distance between the shears and downcoiler downstream due to the consequent dangers of blockages of the leading end of the rolled stock, and the problems of losing temperature due to radiance.
There is also the problem of the trailing end of the wound strip which knocks against the equipment during the braking step of the coil. It is also a problem to support the coiling mandrel as a cantilever.
A further problem is how to guide the strip without causing damage to the surface thereof.
Document JP-A-1157713 describes a coiling device comprising two coiling mandrels onto which a rolled strip is alternately coiled.
The coiling of the strip begins with a first mandrel in a first position; then, after some coils of strip have been coiled, a turntable rotates and inverts the positions of the mandrels, while the strip continues to coil onto the first mandrel.
The first mandrel moves to a position to complete coiling and to discharge the coil, while a second mandrel moves to a start-of-coiling position.
When the coil has reached the desired size on the first mandrel, a shearing assembly arranged upstream intervenes on the strip and the leading end thereof is diverted towards the second, empty mandrel, also because there is a deflector roller and a lower guide.
Between the shearing assembly and the turntable there is a guide blade, the function of which is to distribute and deflect the leading end of the sheared strip in order to send it in the direction of the new mandrel, keeping the trailing end of the strip guided in the direction of the mandrel which is completing the coiling.
To this end, the guide blade has a triangular shape defining a peak facing the shearing means and the deflector roller, the peak being defined by two sides, an upper side cooperating with the lower face of the strip and with the mandrel which is completing the coiling, and a lower side cooperating with the upper face of the strip and with the new mandrel.
The upper side has no pneumatic supporting means and its only function is to prevent the final extremity of the trailing end of the strip from falling downwards, functioning substantially as a supporting base for the said trailing end during the end-of-coiling step.
The lower side, on the contrary, is supplied with pneumatic blowing means which serve first to deflect and then to press the leading end of the sheared strip against a lower guide during the start-of-coiling step on the new mandrel.
The solution of JP'713 does not solve any of the shortcomings explained above; on the contrary, it accentuates them by causing the strip to slide both on the upper side of the guide and also on the lower guide onto which the strip is pressed; nor does it control in any way the knocking of the trailing end when the coil is braked.
The present applicants have designed, tested and embodied this invention to overcome the shortcomings of the state of the art by providing a functional and extremely efficient solution both operationally and in terms of the quality of the product.